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1.
Tetyana Levchenko Yuri Plyuto Nina Kovtyukhova 《Journal of Sol-Gel Science and Technology》2007,43(3):269-274
Possibility of the post-synthesis functionalisation of the template-free and template-structured silica films of ca. 200 nm
thickness on glass slides was evaluated. The films were prepared by dip-coating from TEOS sol–gel precursor in the absence
or presence of CTAB template. It has been found out that the template-structured silica films can be functionalised with Ag
nanoparticles via [Ag(NH3)2]NO3 ion-exchange or with adsorbed Methylene Blue (MB) cationic dye due to the presence of the well-organised mesopores after
template removal. In contrast, only the external geometric surface of the template-free silica films appeared to be accessible
for modifier molecules. Possibility of functionalisation of the multi-layered template-structured silica film depends on the
sequence of dip-coating and calcination steps upon their preparation. When preparation includes reiteration of dip-coating
and calcination steps, only the latest top silica film appears to be accessible to modifier molecules. When preparation includes
successive dip-coating cycles accomplished by calcination of the final multi-layered film, all pores appear to be accessible
since their formation occurs via simultaneous removal of the template molecules over the whole thickness of the multi-layered
template-structured silica film. 相似文献
2.
Hollow silica spheres with mesoporous wall have been synthesized with only ionic liquid ([Dmim]Cl) as the template, and meanwhile, prism-like silica tubes with mesoporous wall have been constructed with the ionic liquid and a nonionic surfactant (P123) as the co-template via sol-gel method for the first time. 相似文献
3.
Nicolas Plumeré Bernd Speiser Prof. Dr. Hermann A. Mayer Prof. Dr. Dominik Joosten Dr. Lars Wesemann Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(4):936-946
A general method for the functionalization of silica surfaces with silicon hydride (Si–H) groups is described for four different preparations of silica. The silica surface is reduced in a two‐step chlorination–reduction procedure within a simple gas‐flow system at high temperatures. After initial dehydroxylation of the silica surface, silicon chloride groups are formed by the reaction with thionyl chloride. The chlorination activates otherwise inaccessible surface siloxane moieties. A high silicon–hydride surface concentration results from the subsequent reduction of the chlorinated surface with hydrogen. The physical properties of the resulting silica are analyzed using scanning electron microscopy, as well as dynamic light scattering and Brunauer–Emmet–Teller measurements. The chlorination–reduction sequence has no significant impact on the structure, surface area and mesopore size of the silica materials used. The surface of the materials is characterized by diffuse reflectance infrared Fourier transform (DRIFT) and 29Si CP/MAS NMR spectroscopy. The silicon–hydride groups are mostly of the ‐type. The use of high temperatures (>800 °C) results in the condensation of internal and surface silanol groups. Therefore, materials with both a fully condensed silica matrix as well as a surface free of silanol groups are obtained. The materials are ideal precursors for further molecular silica surface modification, as demonstrated with a ferrocene derivative. 相似文献
4.
Zhen Li Liqiang Zheng Na Li Shuhua Han Ganzuo Li 《Journal of Dispersion Science and Technology》2013,34(7):1029-1034
This article reports a novel preparation of wormlike mesoporous silica with 1-hexadecane-3-methylimidazolium bromide (C16MIM)Br, a kind of room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The characterization studies were carried out in contrast with that of the mesoporous silica with cetyltrimethylammonium bromide (CTAB), a usually used template, which has the same alkyl chain length with (C16MIM)Br. The structures of the silica materials have been characterized by Transmission electron microscopy (TEM), High-resolution TEM (HRTEM) and N2 adsorption-desorption measurements. The results show that both the mesoporous materials prepared with different templates respectively can form regular wormlike mesopores with ca. 2 nm in pore diameter. They also have large BET surface areas with narrow size distribution. Compared to the CTAB-template mesoporous silica, the material with (C16MIM)Br as a template has highly uniform pore size and larger surface area. In addition, the formation mechanism of the wormlike mesopores with RTIL has been proposed by an electrostatic charge matching assembly-pathway and steric factor. 相似文献
5.
通过焙烧将分散在多孔氧化硅母体中的硝酸镁转化成高分散的MgO物种, 然后使用四丙基氢氧化铵(TPAOH)作为结构导向剂, 将含MgO 的母体通过水热晶化合成MgO/silicalite-1 分子筛复合物. X 射线衍射(XRD)、能量X射线光谱(EDX)和透射电镜(TEM)的结果表明MgO物种被均匀地分散在silicalite-1 分子筛晶体中. 将酸处理脱除氧化镁前后的样品在100%水蒸汽800℃ 条件下老化, 结果表明MgO 的引入有效地提高了分子筛的水热稳定性. 此外, 酸洗脱除MgO/silicalite-1分子筛中的MgO提高了分子筛结晶度, 同时引入了一定的介孔. N2物理吸附-脱附数据证明了酸洗后分子筛中介孔的存在. 水热稳定性的提高和介孔的引入对于在高温下保持催化剂的孔道结构, 提高催化剂的抗积碳能力, 降低催化剂的失活速率以及延长催化剂的使用寿命起着非常重要的作用. 相似文献
6.
A New Synthetic Route to Microporous Silica with Well‐Defined Pores by Replication of a Metal–Organic Framework 下载免费PDF全文
Dr. Atsushi Kondo Dr. Anthony Shoji Hall Prof. Thomas E. Mallouk Prof. Kazuyuki Maeda 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(34):12148-12152
Microporous amorphous hydrophobic silica materials with well‐defined pores were synthesized by replication of the metal–organic framework (MOF) [Cu3(1,3,5‐benzenetricarboxylate)2] (HKUST‐1). The silica replicas were obtained by using tetramethoxysilane or tetraethoxysilane as silica precursors and have a micro–meso binary pore system. The BET surface area, the micropore volume, and the mesopore volume of the silica replica, obtained by means of hydrothermal treatment at 423 K with tetraethoxysilane, are 620 m2g?1, 0.18 mL g?1, and 0.55 mL g?1, respectively. Interestingly, the silica has micropores with a pore size of 0.55 nm that corresponds to the pore‐wall thickness of the template MOF. The silica replica is hydrophobic, as confirmed by adsorption analyses, although the replica has a certain amount of silanol groups. This hydrophobicity is due to the unique condensation environment of the silica precursors in the template MOF. 相似文献
7.
G. Satishkumar 《Journal of solid state chemistry》2009,182(10):2822-608
The formation of polycrystalline tin oxide nanoparticles (NP) and nanowires was investigated using nanocasting approach included solid-liquid strategy for insertion of SnCl2 precursor and SBA-15 silica as a hard template. HR-TEM and XRD revealed that during the thermal treatment in air 5 nm tin oxide NP with well defined Cassiterite structure were formed inside the SBA-15 matrix mesopores at 250 °C. After air calcination at 700 °C the NP assembled inside the SBA-15 mesopores as polycrystalline nanorods with different orientation of atomic layers in jointed nanocrystals. It was found that the structure silanols of silica matrix play a vital role in creating the tin oxide NP at low temperature. The pure tin chloride heated in air at 250 °C did not react with oxygen to yield tin oxide. Tin oxide NP were also formed during the thermal treatment of the tin chloride loaded SBA-15 in helium atmosphere at 250 °C. Hence, it is well evident that silanols present in the silica matrix not only increase the wetting of tin chloride over the surface of SBA-15 favoring its penetration to the matrix pores, but also react with hydrated tin chloride according to the proposed scheme to give tin oxide inside the mesopores. It was confirmed by XRD, N2-adsorption, TGA-DSC and FTIR spectra. This phenomenon was further corroborated by detecting the inhibition of SnO2 NP formation at 250 °C after inserting the tin precursor to SBA-15 with reduced silanols concentration partially grafted with tin chloride. 相似文献
8.
Selective Functionalization of Hollow Nanospheres with Acid and Base Groups for Cascade Reactions 下载免费PDF全文
Dr. Jinsuo Gao Xueying Zhang Yong Lu Prof. Shaomin Liu Dr. Jian Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(20):7403-7407
The inner‐surface functionalization of hollow silica spheres has rarely been reported and is still a challenging topic. Herein, we report a deacetalization–Henry cascade reaction catalyzed by dual‐functionalized mesoporous silica hollow nanospheres with basic amine groups (?NH2) on the internal shell and carboxylic acid groups (?COOH) on the external shell. The selective functionalization has been realized by a combination of “step‐by‐step post‐grafting” and “cationic surfactant‐assisted selective etching” strategy. Compared to unisolated catalyst, the selectively isolated acidic and basic dual catalyst provides excellent catalytic performance for the deacetalization–Henry cascade reaction in terms of both activity (>99 %) and selectivity (95 %). 相似文献
9.
Marie Ernstsson Andra Dedinaite Orlando J. Rojas Per M. Claesson 《Surface and interface analysis : SIA》2023,55(1):26-40
X-ray photoelectron spectroscopy (XPS) was employed to quantify adsorption of polyelectrolytes from aqueous solutions of low ionic strength onto mica, glass, and silica. Silica surfaces were conditioned in base or in acid media as last pre-treatment step (silica-base last or silica-acid last, respectively). Consistency in the determined adsorbed amount, Γ, was obtained independent of the choice of XPS mode and with the two quantification approaches used in the data evaluation. Under the same adsorption conditions, the adsorbed amount, Γ, varied as Γmica > Γsilica-base last ≈ Γglass > Γsilica-acid last. In addition, the adsorbed amount increased with decreasing polyelectrolyte charge density (100% to 1% of segments being charged) for all substrates. Large adsorbed amount was measured for low-charge density polyelectrolytes, but the number of charged segments per square nanometer was low due to steric repulsion between polyelectrolyte chains that limited the adsorption. The adsorbed amount of highly charged polyelectrolytes was controlled by electrostatic interactions and thus limited to that needed to neutralize the substrate surface charge density. For silica, the adsorbed amount depended on the cleaning method, suggesting that this process influenced surface concentration and fraction of different silanol groups. Our results demonstrate that for silica, a higher density and/or more acidic silanol groups are formed using base, rather than acid, treatment in the last step. 相似文献
10.
Periodically Arranged Arrays of Dendritic Pt Nanospheres Using Cage‐Type Mesoporous Silica as a Hard Template 下载免费PDF全文
Kenya Kani Dr. Victor Malgras Dr. Bo Jiang Dr. Md. Shahriar A. Hossain Prof. Saad M. Alshehri Prof. Tansir Ahamad Dr. Rahul R. Salunkhe Dr. Zhenguo Huang Prof. Yusuke Yamauchi 《化学:亚洲杂志》2018,13(1):106-110
Dendritic Pt nanospheres of 20 nm diameter are synthesized by using a highly concentrated surfactant assembly within the large‐sized cage‐type mesopores of mesoporous silica (LP‐FDU‐12). After diluting the surfactant solution with ethanol, the lower viscosity leads to an improved penetration inside the mesopores. After Pt deposition followed by template removal, the arrangement of the Pt nanospheres is a replication from that of the mesopores in the original LP‐FDU‐12 template. Although it is well known that ordered LLCs can form on flat substrates, the confined space inside the mesopores hinders surfactant self‐organization. Therefore, the Pt nanospheres possess a dendritic porous structure over the entire area. The distortion observed in some nanospheres is attributed to the close proximity existing between neighboring cage‐type mesopores. This new type of nanoporous metal with a hierarchical architecture holds potential to enhance substance diffusivity/accessibility for further improvement of catalytic activity. 相似文献
11.
Albert Theolier Agnès Choplin Lindora DOrnelas Jean-Marie Basset Gianmaria Zanderighi C. Sourisseau 《Polyhedron》1983,2(2):119-121
Ru3(CO)12, supported on silica in the absence of oxygen, reacts with silanol groups of the surface to produce a grafted cluster , which has been characterized by IR and Raman spectroscopy; the molecular formula of this cluster is in agreement with the stoichiometric balance of CO evolved during its formation from Ru3(CO)12. The grafted cluster is an intermediate step to produce by thermal decomposition small metallic ruthenium particles of 14 Å together with some Ru(II) carbonyl species encapsulated in the silica surface. 相似文献
12.
Oliveira RL Zanchet D Kiyohara PK Rossi LM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(16):4626-4631
The immobilization of gold nanoparticles (Au NPs) on silica is made possible by the functionalization of the silica surfaces with organosilanes. Au NPs could only be stabilized and firmly attached to silica-support surfaces that were previously modified with amino groups. Au NPs could not be stabilized on bare silica surfaces and most of the NPs were then found in the solution. The metal-support interactions before and after the Au NP formation, observed by X-ray absorption fine structure spectroscopy (XAFS), indicate a stronger interaction of gold(III) ions with amino-modified silica surfaces than with the silanol groups in bare silica. An amino-modified, silica-based, magnetic support was used to prepare an active Au NP catalyst for the chemoselective oxidation of alcohols, a reaction of great interest for the fine chemical industry. 相似文献
13.
Liu JY Wang JG Li N Zhao H Zhou HJ Sun PC Chen TH 《Langmuir : the ACS journal of surfaces and colloids》2012,28(23):8600-8607
Mesoporous zeolite silicalite-1 and Al-ZSM-5 with intracrystalline mesopores were synthesized with polyelectrolyte-surfactant complex as the template. Complex colloids were first formed by self-assembly of the anionic polymer poly(acrylic acid) (PAA) and the cationic surfactant cetyltrimethylammonium bromide (CTAB) in basic solution. During the synthesis procedure, upon the addition of the silica source, microporous template (tetrapropylammonium hydroxide), and NaCl, these PAA/CTA complex colloids underwent dissociation and gave rise to the formation of hollow silica spheres with mesoporous shells templated by CTAB micelles and PAA domains as the core. Under hydrothermal treatment, the hollow silica spheres gradually merged together to form larger particles with the PAA domains embedded as the space occupant, which acted as a template for intracrystalline mesopores during the crystallization of the zeolite framework. Amphiphilic organosilane was used to enhance the connection between the PAA domain and the silica phase during the synthesis. After calcination, single crystal-like zeolite particles with intracrystalline mesopores of about 5-20 nm were obtained, as characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and N(2) adsorption measurements. With the addition of an aluminum source in the synthesis, mesoporous zeolite Al-ZSM-5 with intracrystalline mesopores was also synthesized, and enhanced catalytic property was observed with mesoporous Al-ZSM-5 in acetalization of cyclohexanone with methanol. 相似文献
14.
Lujza-P. Szabó Làszló Szotyory Dènes Kalló Bélafiné-B. Katalin Endre Nagy 《Mikrochimica acta》2000,134(3-4):205-213
Zeolite A, a material of crystalline character, and Hypersil silica have been used as support for the preparation of chiral
stationary phases. On the amorphous silica support surface the silanol groups are randomly dispersed. The crystalline zeolite
secondary building units consisting primarily of SiO4, AlO4
− tetrahedra determine the regularity of surface silanol groups. Owing to the crystal lattice structure, the location of silanols
is well determined and hence the dispersion of chiral selector molecules chemically bonded onto the zeolite surface silanol
groups is fundamentally arranged. Amides of DNB-L-Leu, DNB-L-Phe, B-L-Leu chiral selector molecules were anchored onto the
zeolite silanols and B-L-Leu onto the silica support silanols. Lipophilic buffer in RP conditions has dynamically modified
the residual silanols of each support. The enantioseparation of ion paired D,L-mandelic acid from aqueous solution on the
zeolite and silica supported chiral stationary phases prove a superior enantioseparation on the zeolite supported phases.
Revision February 18, 2000. 相似文献
15.
Novel and innovative hierarchical analcime zeolites were prepared by adding a gemini surfactant which acted as a dual‐functional template. Through a one‐step hydrothermal process, a hierarchical analcime zeolite with abundant intracrystalline mesopores was synthesized. Powder X‐ray diffraction and N2 adsorption–desorption data show that the mesoporous composites possess both a quite a number of mesopores and analcime structure. The results suggest that the dual‐functional template can be effective in the synthesis of hierarchical analcime zeolites. 相似文献
16.
Qiao WM Song Y Hong SH Lim SY Yoon SH Korai Y Mochida I 《Langmuir : the ACS journal of surfaces and colloids》2006,22(8):3791-3797
Mesoporous carbons (MCs) with a high surface area (up to 900 m2/g), large pore volume (up to 2.1 cm3/g), high mesopore ratio (94%), and high yield (70%) were successfully prepared from an AR mesophase pitch, using a commercially nanosized silica template. The removal of the template provided some larger mesopores of 25-50 nm (pore I) with a surface area of ca. 300 m2/g, while the successive carbonization opened the closed pores within the carbon body to give smaller mesopores of 2-10 nm (pore II) with a similar surface area. During the carbonization of pitch precursor, the evaporation of volatile components swells the carbon to introduce the second mesopores among the domains and even microdomain units because of their rearrangements and overlappings in the process. The addition of iron salt with the silica template resulted in a remarkable increase of the surface area (ca. 300 m2/g) by introducing mesopores of 3-5 nm. The resultant MCs maintained some graphitizable natures derived from the anisotropic precursor. Their graphitization at 2400 degrees C provided the graphitic structure with large surface areas (270-460 m2/g) and mesoporosity. 相似文献
17.
Tian WH Sun LB Song XL Liu XQ Yin Y He GS 《Langmuir : the ACS journal of surfaces and colloids》2010,26(22):17398-17404
Copper species were incorporated into SBA-15 by solid-state grinding precursor with as-prepared mesoporous silica (SPA). The obtained materials (CuAS) were well-characterized by XRD, TEM, N(2) adsorption, H(2)-TPR, IR, and TG and compared with the material derived from calcined SBA-15 (CuCS). Surprisingly, CuO up to 6.7 mmol·g(-1) can be highly dispersed on SBA-15 by use of SPA strategy. Such CuO forms a smooth layer coated on the internal walls of SBA-15, which contributes to the spatial order and results in less-blocked mesopores. However, the aggregation of CuO takes place in CuCS material containing 6.7 mmol·g(-1) copper, which generates large CuO particles of 21.4 nm outside the mesopores. We reveal that the high dispersion extent of CuO is ascribed to the abundant silanols, as well as the confined space between template and silica walls provided by as-prepared SBA-15. The SPA strategy allows template removal and precursor conversion in one step, avoids the repeated calcination in conventional modification process, and saves time and energy. We also demonstrate that the CuAS material after autoreduction exhibits much better adsorptive desulfurization capacity than CuCS. Moreover, the adsorption capacity of regenerated adsorbent can be recovered completely. 相似文献
18.
Rosenholm JM Czuryszkiewicz T Kleitz F Rosenholm JB Lindén M 《Langmuir : the ACS journal of surfaces and colloids》2007,23(8):4315-4323
The concentration and Br?nsted acidity of surface silanol groups on mesoporous silica (SBA-15) has been studied by following the adsorption of benzylamine, BA, from water as a function of pH. The adsorbed amount of BA from water was compared to the maximum amount of BA that could be adsorbed from cyclohexane. Furthermore, the surface concentration and acidity of carboxylic acid functions on surface-functionalized SBA-15 was also studied, which allowed the relative surface concentration of remaining silanols to be obtained. Two types of silanols can be identified, where about 1/5 of the silanols have a pKa = 2 and the remaining 4/5 of the silanols have a pKa of about 8.2. According to the literature, these two types of silanols can be identified as Q3 and Q2 silanols, respectively, of which the Q3 silanols are more acidic. For the surface-functionalized materials, pKa values close to their respective intrinsic values are found for the carboxylic acid functions. However, irrespective of the method of surface functionalization, 50% or more of the accessible surface groups are silanols. The results thus suggest that the effective charge density is largely controlled by the (de)protonation of the silanol groups even for surface-functionalized mesoporous silica, which render the surface chemistry of the surface-functionalized silicas to be radically different from what simple schematic representations would suggest. The results are suggested to be of importance for reaching a predictive level of understanding for the behavior of mesoporous silica in a range of applications, as many of the foreseen applications for mesoporous silica involves water as the medium. 相似文献
19.
Fanny Barbotin Roger Spitz Christophe Boisson 《Macromolecular rapid communications》2001,22(17):1411-1414
The synthesis of a series of neodymium complexes supported on modified silica is reported. In an initial step the silanol groups were masked by a Lewis acid (BCl3, AlCl3, TiCl4, ZrCl4, SnCl4, SbCl5, HfCl4), and then a soluble arene complex Nd(η6‐C6H5Me)(AlCl4)3 formed in situ was reacted with the modified silica. The supported complexes are active and highly stereospecific for butadiene polymerization; 1,4‐cis insertion is superior by 99%. The catalyst based on a treatment of silica with BCl3 is the most efficient. 相似文献
20.
T. F. Kuznetsova A. I. Rat’ko S. I. Eremenko 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2012,86(10):1618-1622
Micromesoporous samples of SiO2 were synthesized by the sol-gel method using tetraethoxysilane as a starting reagent and 1–5 wt % cetylpyridinium chloride as a template under the conditions of preadsorption of colloid silica by polyethyleneglycol macromolecules. The adsorption and texture of the samples were studied by the low-temperature nitrogen adsorption-desorption technique. Preadsorption of silica sol was shown to affect the adsorption and capillary-condensation properties of silica. The surface area and the volume of mesopores increased at cetylpyridinium concentrations higher than 1 wt %. The micropore volume increased to a maximum. The capillary-condensation hysteresis loop of H4 type transformed into an H3 loop according to the IUPAC classification. 相似文献